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Abstract:

The present invention provides a technical scheme for forwarding data
packets from one or more user terminals in a relay station, and a
technical scheme for decoding the multiple data packets from the user
terminals in a base station. The relay station performs network encoding
on copies of multiple user terminal packets from one or more user
terminals to obtain a network encoded data packet and sends the data
packet to the base station. The base station receives copies of multiple
user terminal packets from one or more user terminals, respectively, and
a network encoded data packets from the relay station, and performs joint
soft combining and decoding on them.

Claims:

1. A method of decoding data packets from user terminals in a base
station of a wireless communication network, comprising the following
steps: A. receiving copies of multiple user terminal packets from one or
more user terminals and a network encoded data packet from a relay
station, wherein said network encoded data packet is obtained after said
relay station performs network coding on said copies of multiple user
terminal packets respectively received from said one or more user
terminals; B. performing joint soft combining and decoding on said copies
of multiple user terminal packets and said network encoded data packet.

2. A method according to claim 1, wherein said step of performing joint
soft combining and decoding comprises the following steps: B1. obtaining
an initial soft information sequence of encoded bit sequence of said
network encoded data packet and an estimated soft information sequence of
an encoded bit sequence or an initial soft information sequence of the
encoded bit sequence of said copies of multiple user terminal packets;
B2. performing joint soft combining processing on said initial soft
information sequence of the encoded bit sequence of said network encoded
data packet and said estimated soft information sequence of the encoded
bit sequence or said initial soft information sequence of the encoded bit
sequence of said copies of multiple user terminal packets, so as to
obtain a soft combined bit likelihood ratio sequence of the bit sequence
of at least one user terminal data packet of said multiple user terminal
data packets; B3. performing channel decoding on said soft combined bit
likelihood ratio sequence.

3. A method according to claim 2, wherein said network encoding comprises
performing bitwise XOR processing on multiple bit sequence obtained after
performing channel decoding on said copies of multiple user terminal data
packets, said step B2 comprises the following step: performing soft
combining processing according to equation L L ~ R ( b 1 )
= L L ^ R ( b 1 ) + log oddc LLR (
oddc ) evenc LLR ( evenc ) , ##EQU00013##
wherein b1 is an encoded bit in a user terminal data packet, L{tilde
over (L)}R(b1) is the soft combined bit likelihood ratio after
performing soft combining on the encoded bit, L{circumflex over
(L)}R(b1) is an estimated bit likelihood ratio of the encoded bit,
LLR(oddc) is a combination of an odd number of bit likelihood ratios out
of estimated likelihood ratios L{circumflex over (L)}R(b2),
L{circumflex over (L)}R(b3), L{circumflex over (L)}R(bm) of
corresponding encoded bits b2, b3, . . . bm of other user
terminal data packets with which XOR processing is performed on the
encoded bit b1 and an initial bit likelihood ratio of corresponding
encoded bit bNC in said network encoded data packet, oddc
LLR ( oddc ) ##EQU00014## is the sum of all e raised to the power
of the combinations of an odd number of bit likelihood ratios
combinations, bNC=b.sub.1.sym.b.sub.2.sym. . . . ⊕bm, m is
the number of the user terminals; LLR(evenc) is a combination of an even
number of bit likelihood ratios out of estimated likelihood ratios
L{circumflex over (L)}R(b2), L{circumflex over (L)}R(b3),
L{circumflex over (L)}R(bm) of corresponding encoded bits b2,
b3, . . . bm of the other user terminal data packets with which
XOR processing is performed on the encoded bit b1 and the initial
bit likelihood ratio of the corresponding encoded bit bNC in said
network encoded data packet, evenc LLR ( evenc )
##EQU00015## is the sum of all e raised to the power of the combinations
of bit likelihood ratios.

5. A method according to claim 1, wherein said network encoding comprises
performing, by said relay station, multiplication transforming in the
binary domain on at least one of multiple bit sequences obtained after
performing channel decoding on said copies of multiple user terminal data
packets received by it, and then performing adding transforming
processing in the binary domain with other bit sequences; or performing
bitwise XOR or XNOR processing on the multiple bit sequences.

6. A method according to claim 2, further comprising the following steps
before said step B2: performing channel decoding on the initial soft
information sequence of the encoded bits of said copies of multiple user
terminal data packets; for user terminal data packets that is channel
decoded incorrectly, performing the operations of said step B2, B3.

7. A method of forwarding data packets from multiple user terminals in a
relay station of a wireless communication network, comprising the
following steps: receiving copies of multiple data packets from one or
more user terminal, respectively; performing network encoding processing
on said copies of multiple data packets, to obtain a network encoded data
packet; sending said network encoded data packet to a base station.

8. A method according to claim 7, wherein said network encoding
processing comprises any one of the following steps: performing
multiplication transforming in the binary domain on at least one of
multiple bit sequences obtained after performing channel decoding on said
copies of multiple data packets, and then performing adding transforming
processing in the binary domain with other bit sequences; said network
encoding comprises performing bitwise XOR or XNOR processing on multiple
bit sequences after performing channel decoding on said copies of
multiple data packets.

9. A decoding apparatus for decoding data packets from user terminals in
a base station of a wireless communication network, comprising: a first
receiving unit for receiving copies of multiple user terminal packets
from one or more user terminals and a network encoded data packet from a
relay station, wherein said network encoded data packet is obtained after
said relay station performs network encoding on said copies of multiple
user terminal packets respectively received from said one or more user
terminals; a soft combining and decoding unit for performing joint soft
combining and decoding on said copies of multiple user terminal packets
and said network encoded data packet.

10. A decoding apparatus according to claim 9, wherein said soft
combining and decoding unit comprises: an obtaining unit for obtaining an
initial soft information sequence of encoded bit sequence of said network
encoded data packet and an estimated soft information sequence of an
encoded bit sequence or an initial soft information sequence of the
encoded bit sequence of said copies of multiple user terminal packets; a
soft combining processing unit for performing joint soft combining
processing on said initial soft information sequence of the encoded bit
sequence of said network encoded data packet and said estimated soft
information sequence of the encoded bit sequence or said initial soft
information sequence of the encoded bit sequence of said copies of
multiple user terminal packets, to obtain a soft combined bit likelihood
ratio sequence of the bit sequence of at least one user terminal data
packet of said multiple user terminal data packet; a channel decoding
unit for performing channel decoding on said soft combined bit likelihood
ratio sequence.

11. A decoding apparatus according to claim 10, wherein said network
encoding comprises performing bitwise XOR processing on multiple bit
sequence obtained after performing channel decoding on said copies of
multiple user terminal data packets, said soft combining processing unit
is for: performing soft combining processing according to equation L
L ~ R ( b 1 ) = L L ^ R ( b 1 ) + log
oddc LLR ( oddc ) evenc LLR ( evenc )
, ##EQU00017## wherein b1 is an encoded bit in a user terminal data
packet, L{tilde over (L)}R(b1) is the soft combined bit likelihood
ratio after performing soft combining on the encoded bit, L{circumflex
over (L)}R(b1) is an estimated bit likelihood ratio of the encoded
bit, LLR(oddc) is a combination of an odd number of bit likelihood ratios
out of estimated likelihood ratios L{circumflex over (L)}R(b2),
L{circumflex over (L)}R(b3), L{circumflex over (L)}R(bm) of
corresponding encoded bits b2, b3, . . . bm of other user
terminal data packets with which XOR processing is performed on the
encoded bit b1 and an initial bit likelihood ratio of corresponding
encoded bit bNC in said network encoded data packet, oddc
LLR ( oddc ) ##EQU00018## is the sum of all e raised to the power
of the combinations of odd numbers of bit likelihood ratios combinations,
bNC=b.sub.1.sym.b.sub.2.sym. . . . ⊕bm, m is the number of
the user terminals; LLR(evenc) is a combination of an even number of bit
likelihood ratios out of estimated likelihood ratios L{circumflex over
(L)}R(b2), L{circumflex over (L)}R(b3), L{circumflex over
(L)}R(bm) of corresponding encoded bits b2, b3, . . .
bm of the other user terminal data packets with which XOR processing
is performed on the encoded bit b1 and the initial bit likelihood
ratio of the corresponding encoded bit bNC in said network encoded
data packet, evenc LLR ( evenc ) ##EQU00019## is the sum
of all e raised to the power of the combinations of even numbers of bit
likelihood ratios combinations.

13. A decoding apparatus according to claim 9, wherein said network
encoding comprises performing, by said relay station, multiplication
transforming in the binary domain on at least one of multiple bit
sequences obtained after performing channel decoding on said copies of
multiple user terminal data packets received by it, and then performing
adding transforming processing in the binary domain with other bit
sequences; or performing bitwise XOR or XNOR processing on the multiple
bit sequences.

14. A decoding apparatus according to claim 10, wherein said channel
decoding unit is further for: performing channel decoding on the initial
soft information sequence of the encoded bits of said copies of multiple
user terminal data packets; for user terminal data packets that is
channel decoded incorrectly, performing soft combining processing by said
soft combining processing unit and performing channel decoding on the bit
likelihood sequence obtained after performing by said soft combining
processing unit.

15. A forwarding apparatus for forwarding data packets from multiple user
terminals in a relay station of a wireless communication network,
comprising: a second receiving unit for receiving copies of multiple data
packets from one or more user terminal, respectively; a network encoding
unit for performing network encoding processing on said copies of
multiple data packets, to obtain a network encoded data packet; a sending
unit for sending said network encoded data packet to a base station.

16. (canceled)

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to a wireless relay communication
network, more particularly, to data packet forwarding in a relay station
and data packet decoding in a base station in the wireless relay
communication network.

BACKGROUND OF THE INVENTION

[0002] In LTE-A wireless communication network, relay is considered as an
important technical means to support increasing capacity and enlarging
coverage range. In uplink relay, information from multiple user terminals
needs to be relayed. Generally, information from each user terminal is
respectively relayed to eNodeB node. For example, in FIG. 1, relay
station 21 respectively relays data packets P1 and P2 respectively from
user terminals 11 and 12 to eNodeB node 31. For the two data packets P1
and P2, resources comparable to the length of the two packets are
required to carry them. Since radio resources of communication links are
very limited in wireless communication network, it is necessary to apply
some schemes for saving radio resources to perform relay.

SUMMARY OF THE INVENTION

[0003] Based on the technical background, the present invention provides a
technical scheme for forwarding data packets from one or more user
terminals in a relay station, and a technical scheme for joint soft
combining and decoding the data packets from user terminals in a base
station.

[0004] According to an embodiment of the present invention, a method of
decoding data packets from user terminals in a base station of a wireless
communication network is provided. The method comprises the following
steps of: receiving copies of multiple user terminal packets from one or
more user terminals and a network encoded data packet from a relay
station, wherein said network encoded data packet is obtained after said
relay station performs network encoding on the copies of multiple user
terminal packets respectively received from said one or more user
terminal; performing joint soft combining and decoding on said copies of
multiple user terminal packets and said network encoded data packet.

[0005] According to another embodiment of the present invention, a method
of forwarding data packets from multiple user terminals in a relay
station of a wireless communication network is provided. The method
comprises the following steps of: receiving copies of multiple data
packets from one or more user terminals, respectively; performing network
encoding processing on said copies of multiple data packets, so as to
obtain a network encoded data packet; sending said network encoded data
packet to a base station.

[0006] According to yet another embodiment of the present invention, a
decoding apparatus for decoding data packets from user terminals in a
base station of a wireless communication network is provided. The
decoding apparatus comprises: a first receiving unit for receiving copies
of multiple user terminal packets from one or more user terminals and a
network encoded data packet from a relay station, wherein said network
encoded data packet is obtained after said relay station performs network
encoding on said copies of multiple user terminal packets respectively
received from said one or more user terminals; a soft combining and
decoding unit for performing joint soft to combining and decoding on said
copies of multiple user terminal packets and said network encoded data
packet.

[0007] According to a further embodiment of the present invention, a
forwarding apparatus for forwarding data packets from multiple user
terminals in a relay station of a wireless communication network is
provided. The forwarding apparatus comprises: a second receiving unit for
receiving copies of multiple data packets from one or more user
terminals, respectively; a network encoding unit for performing network
encoding processing on said copies of multiple data packets, so as to
obtain a network encoded data packet; a sending unit for sending said
network encoded data packet to a base station.

[0008] By using the methods and apparatus of the present invention, radio
frequency resources of uplink communication links are efficiently saved,
and power consumption in relay station is efficiently reduced.

BRIEF DESCRIPTION OF DRAWINGS

[0009] Other features, objectives and advantages of the present invention
will become more apparent from the following detailed description of the
non-limiting embodiments in conjunction with the accompanying drawings.

[0010] FIG. 1 is a diagram of the network topology structure in prior art;

[0011] FIG. 2 is a diagram of forwarding data packets by a relay station
of a wireless communication network according to a detailed embodiment of
the present invention;

[0012] FIG. 3 is a flow diagram of a method of forwarding data packets
from multiple user terminals in a relay station of a wireless
communication network according to a detailed embodiment of the present
invention;

[0013] FIG. 4 is a flow diagram of a method of decoding data packets from
user terminals in a base station of a wireless communication network
according to a detailed embodiment of the present invention;

[0014] FIG. 5 is a flow diagram of a sub-step of step S402 illustrated in
FIG. 4;

[0015] FIG. 6 is a block diagram of decoding in a base station of a
wireless communication network according to a detailed embodiment of the
present invention;

[0016] FIG. 7 is a diagram of forwarding data packets by a relay station
according to another detailed embodiment of the present invention;

[0017] FIG. 8 is a diagram of simulation results of frame error rate
according to a detailed embodiment of the present invention;

[0018] FIG. 9 is a diagram of an application scenario according to another
detailed embodiment of the present invention;

[0019] FIG. 10 is a structural diagram of forwarding apparatus 100 for
forwarding data packets in a relay station of a wireless communication
network according to a detailed embodiment of the present invention;

[0020] FIG. 11 is a structural diagram of decoding apparatus 110 for
decoding data packets from user terminals in a base station of a wireless
communication network according to a detailed embodiment of the present
invention;

[0021] Where, same or similar reference signs refer to same or similar
step features or apparatus (modules).

DETAILED DESCRIPTION OF EMBODIMENTS

[0022] Detailed description of the embodiments of the present invention is
is given below in conjunction with the accompanying drawings.

[0023] FIG. 2 is a diagram of a forwarding scheme of relay station 21
according to a detailed embodiment of the present invention. It is to be
explained that only two user terminals 11 and 12 are illustrated in FIG.
2, but those skilled in the art should understand that the technical
scheme of the present invention is applicable to the scenario of multiple
user terminals, which will be also explained in the below.

[0024] FIG. 3 illustrates a flow diagram of a method, for forwarding data
packets from multiple user terminals by relay 21 in FIG. 2. Detailed
description of the steps illustrated in FIG. 3 is given below in
conjunction with FIG. 2.

[0025] First, in step S301, relay 21 receives copies of data packets
P1 and P2 from user terminals 11 and 12. It is to be explained
that the order of sending data packet P1 by user terminal 11 and
sending data packet P2 by user terminal 12 is not limited, and relay
station 21 receives copies of data packets P1 and P2 as well as
base station 31 receives copies of data packets P1 and P2.

[0026] Next, in step S302, relay station 21 performs network encoding on
to copies of data packets P1 and P2 respectively from user
terminal 11 and 12, so as to obtain a network encoded data packet
PNC. The meaning of network encoding refers to saving transmission
resources by means of encoding data of multiple sources, after
demodulation and channel decoding processing are performed on data
packets of multiple sources. For is example, in the binary domain,
network encoding comprises at least two following types: one is to
perform bitwise XOR or XNOR processing on the multiple bit sequences
obtained after performing channel decoding on the multiple user terminal
data packets, and if the length of each bit sequence is not identical,
the shorter bit sequences are padded with zeros or ones or other
predefined information to achieve the length of the longest bit sequence;
the other is to perform multiplication transforming in the binary domain
on at least one of multiple bit sequences obtained after performing
channel decoding on the multiple user terminal data packets, and then to
perform adding transforming processing in the binary domain with other
bit sequences. Examples for the above two network encoding manners are
respectively described in the below.

[0027] Without loss of generality, it is assumed that the hit sequence
obtained after relay station 21 performs channel decoding on data packet
P1 is 0101100110, which is ten bits in total, and the bit sequence
is the correct bit sequence; the bit sequence obtained after relay
station 21 performs channel decoding on data packet P2 is
1100001100, which is ten bits in total.

[0028] By performing bitwise XOR processing on the above two bit
sequences, the bit sequence of data packet PNC obtained is
1001101010; if XNOR processing is performed, the bit sequence of data
packet PNC obtained is 0110010101.

[0029] By performing an operation of multiplying with 3 in the binary is
domain on the bit sequence of data packet P1, 10000110010, which is
11 bits in total, is obtained. By performing a binary adding processing
on it and the bit sequence of data packet P2, the bit sequence of
data packet PNC obtained is 11100111110.

[0030] Finally, in step S303, relay station 21 sends the network encoded
data packet to base station 31. Specifically, relay station 21 sends it
via a transmitter after performing channel encoding and symbol modulation
on the network encoded data packet.

[0031] It is to be explained that, the network encoding processing is not
limited to be performed in the binary domain and can be performed in the
octal domain, hex domain or decimal domain, for example.

[0032] FIG. 4 shows a flow diagram of a method for decoding a data packet
from user terminals in a base station according to an embodiment of the
present invention. Following in conjunction with FIG. 2, the decoding
procedure to data packets from user terminal 11 or 12 by base station 31
locating in FIG. 2 is described in detail.

[0033] First, in step S401, base station 31 receives a network encoded
data packet from relay station 21, and copies of data packets P1 and
P2 respectively from user terminal 11 and 12, wherein, the network
encoded data packet from relay station 21 is obtained after relay station
21 performs said network encoding mentioned above on the copies of the
two user terminal data packets P1 and P2 received from the user
terminal 11 and 12, respectively.

[0034] Generally, because of processing delay in relay station 21, base
station 31 firstly receives copies of data packets P1 and P2
respectively from user terminal 11 and 12. It is to be explained that,
due to the difference between the wireless communication links from user
terminal 11 or 12 to relay station 21 and from user terminal 11 or 12 to
base station 31, copies of a same data packet P1 or P2 received
by relay station 21 and base station 31 may be different. For example,
because relay station 21 is closer to user terminal 11 or 12, the copy of
data packet P1 or P2 it received can be completely correctly
received; Since base station 31 is farther from user terminal 11 or 12,
the copy of data packet P1 or P2 it received may be mistakenly
received.

[0035] It is to be explained that, the skilled in the field should
understand, specifically, the means of sending data packets P1 and
P2 can be time division, code division, frequency division, space
division etc. Because the means of sending the data packets has no direct
relationship with the present invention, it will not be described in
detail here.

[0036] Thereafter, in step S402, joint soft combining and decoding
processing are performed on copies of user terminal data packets P1
and P2, and on said network encoding data packet PNC.

[0037] FIG. 5 shows a flow diagram of a sub-step of step S402 according to
an embodiment of the present invention.

[0038] First, in step S501, base station 31 obtains an initial soft
information sequence of an encoded bit sequence of network encoded data
packet PNC and an estimated soft information sequence of an encoded
bit sequence or an initial soft information sequence of an encoded bit
sequence of said copies of multiple user terminal packets.

[0039] The following describes in detail the computation procedure to
initial soft information of an encoded bit sequence.

[0040] Without loss of generality, for example, an initial bit likelihood
ratio is taken as initial soft information. Assuming symbol in data
packet P1 sent by user terminal 11 is s1, and then the symbol
received by base station 31 is y.sub.U1,B:

y.sub.U1,B=h.sub.U1,Bs1+n.sub.U1,B (1)

Where, h.sub.U1,B is the channel transfer coefficient from user terminal
11 to base station 31, n.sub.U1,B is a Gaussian distributed noise with
variance σ2, then the likelihood ratio of symbol s1 is:

Where, j, k is the bits contained by each symbol. For example for QPSK
symbol, j, k=1˜2.

[0042] By performing channel decoding after initial soft information
sequence of an encoded bit sequence is input into a channel decoder, the
channel decoder outputs the estimated soft information sequence of the
encoded bit sequence.

[0043] By performing processing of equations (2) and (3) on the network
encoded data packets, an initial soft information sequence of the encoded
bit sequence of the network encoded data packets is obtained.

[0044] In step S502, base station 31 performs joint soft combining
processing on an initial soft information sequence of an encoded bit
sequence of network encoded data packet PNC and an estimated soft
information sequence of an encoded bit sequence or an initial soft
information sequence of an encoded bit sequence of copies of user
terminal packets P1 and P2, so as to obtain a soft combined bit
likelihood ratio of the bit sequence of at least one user terminal data
packet out of said multiple user terminal data packets.

[0045] Optionally, in an embodiment of the present invention, the network
encoding performed in base station 21 is bitwise XOR processing on the
two bit sequences after performing channel decoding on copies P1 and
P2 of user terminal data packets. Joint soft combining can be
performed in base station 31 according to the following equation:

Where, b1 is an encoded bit in user terminal data packet P1,
L{tilde over (L)}R(b1) is the joint soft combining likelihood ratio
after performing soft combining on the encoded bit, L{circumflex over
(L)}R(b1) is an estimated bit likelihood ratio or initial bit
likelihood ratio of the encoded bit, L{circumflex over (L)}R(b2) is
an estimated likelihood ratio of corresponding encoded bit b2 in the
user terminal data packet, on which XOR processing is performed with
encoded bit b1, LLR(bNC) is an initial bit likelihood ratio of
the corresponding encoded bit bNC in network encoded data packet
PNC.

[0046] By taking the approximation theorem log
(ea+eb)≈max(a,b), the above equation can be simplified
to equation (5), so that computation effort of base station 31 can be
greatly reduced.

[0047] Then, in step S503, base station 31 performs channel decoding on
the soft combining bit likelihood ratio obtained according to equation
(4) or (5), so as to obtain a bit sequence of data packet P1 or
P2.

[0048] The following describes in detail the derivation process of
equation (4).

[0049] Suppose s3 is symbol of data packet PNC sent by relay
station 21. The symbol that base station 31 received is y.sub.R,B:

y.sub.R,B=h.sub.R,Bs3+n.sub.R,B (6)

[0050] For example, for bit bNC in data packet PNC that is
obtained after performing XOR processing on bit b1 in data packet
P1 and bit b2 in data packet P2, according to Maximum A
Posteriori (MAP) principle, the bit likelihood of bit b1 can be
expressed by the following equation:

[0051] Where, yNC is the value of the symbol, which is interfered and
attenuated by channel and received by base station 31, when s3 is
the symbol sent by relay station 21. Wherein, character s3 is the
symbol after performing modulation on a bit sequence comprising bit
bNC. For example for QPSK, bNC,1 and bNC,2 two bits are
modulated to one symbol s3.

[0052] Because bNC is obtained by performing XOR on bit b1 in
data packet P1 and bit b2 in data packet P2, the joint
probability on the right side of equation (7) is related to the
probabilities of b1 and b2. Table 1 shows all possible values
of b1, b2 and bNC. The numerator in the right term of
equation (7) shows the probabilities of the two lower lines in table 1,
and the denominator expresses the probabilities of the two upper lines in
table 1.

[0053] According to table 1, equation (8) can be obtained according to
equation (7):

n=1,2 is the bit likelihood ratio of bit bn. If bit bn is not
received, then let P(bn=1)=P(bn=0), Ld(bn)=0. Since
b1 and b2 have already been received, therefore, the initial
bit likelihood ratios of bit b1, b2 or the estimated bit
likelihood ratio output by channel decoder can be used to substitute
Ld(bn), and the latter is preferred. Thus equation (4) or
equation (5) can be obtained.

[0056] Optionally, prior to step S502 as shown in FIG. 5, base station 31
performs channel decoding on an initial bit likelihood ratio sequence of
an encoded bit sequence of data packets P1 and P2. If channel
decoding is performed correctly on both of the data packets, for example
CRC verification results are correct, the data bit sequences of P1
and P2 after channel decoding are stored, and said soft combining
processing as described in step S502 does not need to be performed. If
any data packet, for example the channel decoding of data packet P1,
is not correct, said soft combining processing as mentioned in step S502
needs to be performed on data packet P1. At this time, base station
31 stores the estimated soft information sequence or the initial soft
information sequence of the encoding bit sequence of P1 and P2,
getting ready for the soft combining processing as shown in step S502 on
the initial soft information sequence of the encoded bit sequence of the
network encoded data packet that is received later.

[0057] FIG. 6 shows a diagram of decoding in base station 31 at that time.

[0058] The above describes in detail the derivation procedure of equation
(4) for the application scenario shown in FIG. 1. According to the above
derivation procedure, the skilled in the field can expand the present
invention to normal application scenarios. For example, for the
application scenario shown in FIG. 7, where network encoded PNC is
formed by performing bitwise XOR on copies of three data packets from
user terminals 11, 12 and 13, according to table 2, the following
equation is not difficult to obtain:

[0060] Here, LLR(oddc) is a combination of an odd number of bit likelihood
ratios out of estimated likelihood ratio L{circumflex over
(L)}R(b2), L{circumflex over (L)}R(b3), L{circumflex over
(L)}R(bm) of corresponding encoded bit b2, b3, . . .
bm of other user terminal data packets, with which XOR processing is
performed on encoded bit b1, and a bit likelihood ratio
LLR(bNC) of the initial bit likelihood sequence of corresponding
encoded bit bNC in the network encoded data packet,

oddc LLR ( oddc ) ##EQU00011##

is the sum of all e raised to the power of the combinations of odd
numbers of bit likelihood ratios, bNC=b1⊕b2⊕ . . .
⊕bm, m is the total number of user terminals; LLR(evenc) is a
combination of an even number of bit likelihood ratios out of estimated
likelihood ratios L{circumflex over (L)}R(b2), L{circumflex over
(L)}R(b3), L{circumflex over (L)}R(bm) of corresponding encoded
bits b2, b3, . . . bm of the other user terminal data
packets, with which XOR processing is performed on said encoded bit
b1, and a bit likelihood ratio of the initial bit likelihood ratio
of corresponding encoded bit bNC of the network encoded data packet,

evenc LLR ( evenc ) ##EQU00012##

is the total sum of all e raised to the power of the combinations of bit
likelihood ratios.

[0061] It is to be explained that, equation (4), (5), (10) and (11) are
soft combining processing equations obtained aiming to bitwise XOR
processing. XNOR is the similar operation to XOR. On the basis of
equations (4), (5), (10) and (11) the skilled in the field can easily
obtain the soft combining processing equation corresponding to equation
(4), (5), (10) and (11) in a scenario where bitwise XNOR processing is
performed, and it will not be described here in detail here.

[0062] In another embodiment of the present invention, a weight
coefficient can be added to each bit likelihood ratio in equations (4),
(5), (10) and (11). For example, the bit likelihood ratio coefficient can
be determined by whether the channel quality of the channels for
transmitting each data packet is good or bad. For example, if the channel
is quality of the channel for transmitting data packet P1 is worse
than the channel quality of the channel for transmitting data packet
PNC, then the weight coefficient before L{circumflex over
(L)}R(b1) is smaller than the weight coefficient before L{circumflex
over (L)}R(bNC).

[0063] It is to be explained additionally that, the above describes in
detail the network encoding procedure in relay station 21 and decoding
procedure in base station 31 for data packets P1 and P2
respectively from user terminals 11 and 12. If data packets P1 and
P2 both come from user terminal 11 or 12, the network encoding
procedure in relay station 21 and the decoding procedure in base station
31 are same as above text.

[0064] It is to be further explained that, according to different network
encoding specifically adopted, the style of joint soft combining and
decoding that are performed in base station 21 is also various, not
limited to the above descriptions in said embodiments.

[0065] The soft combining algorithmic in equation (4) or (5) is further
verified by the experiment on the application scenario shown in FIG. 2.
FIG. 8 shows the results of the experiment. The additive Gaussian white
noise Rayleigh wireless communication channel simulation model with unit
variance is adopted in the experiment in FIG. 8. For the purpose of
convenience, suppose the channel transmission coefficients of user
terminals 11 and 12 to relay station 21 or base station 31 are equal, and
the signal noise ratio of user terminal 11 or 12 to the communication
link of base station 31 is 6 dB worse than the signal noise ratio of the
communication link of relay station 21 to base station 31. 3460 bits UMTS
1/3 Turbo codes and QPSK symbol modulation are adopted in channel
encoding. Frame Error Rates (FER) in base station 31 with the present
relay as shown in FIG. 1, with a relay adopting the combining algorithmic
as shown in equation (4) or (5), and without a relay, are respectively
shown in FIG. 8. It can be obviously seen from FIG. 8 that, for the
application scenario shown in FIG. 2, the frame error rate in base
station 31 is evidently lower than the frame error rate without a relay,
but slightly higher than the frame error rate of the present relay as
shown in FIG. 1. However, in comparison to the latter, in the application
scenario shown in FIG. 2, approximately 50% relay resources are saved,
and the power dissipation in relay station 21 is correspondingly reduced.

[0066] It is to be explained that, the present invention is not limited to
the application scenarios shown in FIG. 2 or FIG. 7. For example, data
packets P1 or P2, which is received by base station 31, is not
limited to be sent directly by each user terminal, or probably by a
certain relay station, such as being relayed by relay station 22 as shown
in FIG. 9.

[0067] FIG. 10 shows a structure diagram of forwarding unit 100 used to
forward data packets from multiple user terminals in a relay station of a
wireless communication network according to an embodiment of the present
invention. In FIG. 10, forwarding unit 100 comprises a second receiving
unit 101, network encoding unit 102 and sending unit 103.

[0068] In the following by taking the application scenario shown in FIG. 2
as an example, the forwarding procedures by relay station 21 in FIG. 2 to
data packets P1 and P2 respectively coming from user terminal
11 and 12 are explained in detail.

[0069] Firstly, second receiving unit 101 receives copies of the two data
packets respectively coming from user terminal 11 and 12. It is to be
explained that, the order of sending data packet P1 by user terminal
11 and sending data packet P2 by user terminal 12 is not limited,
and second receiving unit 101 receives copies of data packets P1 and
P2 as well as base station 31 receives copies of data packets
P1 and P2.

[0070] Then, network encoding unit 102 performs network encoding
processing on the copies of data packets P1 and P2 coming from
user terminals 11 and 12, so as to obtain a network encoded data packet
PNC. The meaning of network encoding refers to saving transmission
resources by means of performing encoding on multiple data packets after
performing demodulation, channel decoding to processing on the data
packets of multiple sources. For example, in the binary domain, network
encoding includes at least the following two types: one is to perform
bitwise XOR or XNOR processing on the multiple bit sequences after
performing channel decoding on the multiple user terminal data packets,
if the length of each bit sequence is is not identical, the end of
shorter bit sequences are padded with zero or 1 to achieve the length of
the longest bit sequence; another is to perform adding transforming
processing with the other bit sequences after performing multiplication
transforming in the binary domain on at least one of multiple bit
sequences obtained after performing channel decoding on the data packets
of the multiple user terminals. The following text describes the two
network encodings respectively by examples.

[0071] Without loss of generality, suppose the bit sequence obtained after
relay station 21 performing channel decoding on data packet P1 is
0101100110, which is 10 bits in total, and the bit sequence is the
correct bit sequence; the bit sequence obtained after relay station 21
performing channel decoding on data packet P2 is 1100001100, which is 10
bits in total.

[0072] By performing bitwise XOR processing on the above two bit
sequences, the bit sequence 1001101010 of data packet PNC is
obtained; if XNOR processing is performed, the bit sequence 0110010101 of
data packet PNC is obtained.

[0073] By performing multiplication processing on the bit sequence of data
packet P1 by 3 in the binary domain, 10000110010 is obtained, which
is 11 bits in total, and adding processing in the binary domain is
performed on it with the bit sequence of data packet P2 to get a bit
sequence of data packet PNC, which is 11100111110.

[0075] FIG. 11 shows a structure diagram of decoding unit 110 used to
decode data packet from user terminal in a base station of a wireless
communication network according to an embodiment of the present
invention. In FIG. 11, decoding unit 110 comprises a first receiving unit
111 and soft combing decoding unit 112. In an example of the embodiment,
soft combining decoding unit 112 comprises obtaining unit 1121, soft
combining processing unit 1122 and channel decoding unit 1123, which are
also shown together in FIG. 11. It is understood by the people in the
field that, in FIG. 11, only first receiving unit 111 and soft combining
decoding unit 112 are necessary units, the other units are optional.

[0076] The following takes the application scenario shown in FIG. 2 as an
example, to describe in detail the procedure that base station 31 in FIG.
2 performs decoding on the data packets coming from user terminal 11 or
12.

[0077] First, first receiving unit 111 receives network encoded data
packets from relay station 21, and copies of data packets P1 and
P2 respectively coming from user terminals 11 and 12. Wherein,
network encoded data packet PNC from relay station 21 is obtained by
performing said network encoding mentioned above on the copies of the two
user terminal data packets P1 and P2 respectively received by
relay station 21 from the user terminal 11 and 12.

[0078] Generally, due to the processing delay in relay station 21, first
receiving unit 111 first receives copies of data packets P1 and
P2 respectively coming from user terminals 11 and 12. It should be
explained that, because of the difference of the wireless communication
links from user terminal 11 or 12 to relay station 21 and from user
terminal 11 or 12 to base station 31, the copies of the same data packet
P1 or P2 received by relay station 21 and base station 31 may
be different. For example, because relay station 21 is closer to user
terminal 11 or 12, the copy of data packet P1 or P2 it received
may be completely correct; since base station 31 is farther from user
terminal 11 or 12, the copy of data packet P1 or P2 that first
receiving unit 111 received may be mistakenly received.

[0080] According to an embodiment of the present invention, soft combining
decoding unit 112 comprises three sub-units: obtaining unit 1121, soft
combining processing unit 1122 and channel decoding unit 1123. The
following describes in detail joint soft combining and decoding procedure
of the three sub-units.

[0081] First, obtaining unit 1121 obtains the initial soft information
sequence of the encoded bit sequence of network encoded data packet
PNC, and the initial soft information sequence of encoded bit
sequence or estimated soft information sequence of the encoded bit
sequence of copies of multiple user terminal data packets. The obtaining
procedure of initial soft information or estimated soft information of
encoded bit is described in detail in above text, and will not be
mentioned again here.

[0082] Next, soft combining processing unit 1122 performs soft combining
processing on the initial soft information of the encoded bit sequence of
network encoded data packet PNC, and on the initial soft information
of the encoded bit sequence or the estimated soft information of the
encoded bit sequence of copies of multiple user terminal data packets
P1 and P2, so as to obtain a soft combining likelihood ratio
sequence of the bit sequence of at least one user terminal data packet in
said multiple user terminal data packets.

[0083] Optionally, in an embodiment, if the network encoding executed in
relay station 21 is bitwise XOR processing on two bit sequences after
performing channel decoding on copies of user terminal data packets
P1 and P2, soft combining processing unit 1122 can perform soft
combining processing according to equation (4) or equation (5).

[0084] Finally, channel decoding unit 1123 performs channel decoding on
the soft combining likelihood ratio sequence obtained by soft is
combining processing unit 1122 according to equation (4) and (5), so as
to obtain a bit sequence of data packets P1 or P2.

[0085] Optionally, before soft combining processing unit 1122 and channel
decoding unit 1123 performing above operations, channel decoding unit
1123 performs channel decoding on the initial bit likelihood ratio of
each bit of data packets P1 and P2. If the channel decoding of
the two data packets is correct, for example CRC verification results are
correct, then soft combining processing unit 1122 does not need to
perform said soft combining processing described above according to
equation (4) (5). If the channel decoding of a data packet, such as data
packet P1, is incorrect, soft combining processing unit 1122 needs
to perform soft combining processing on said data packet P1.

[0086] Above describes in detail the embodiments of the present invention.
It should be understood that, the present invention is not limited to the
above specific embodiments, and any variation or modification can be made
by those skilled in the art without departing from the scope of the
appended claims. The technical schemes of the present invention can be
realized by software or hardware.